Modelling stimulus dependencies and temporal characteristics of Gamma Rhythm in Macaque Primary Visual Cortex

Abstract

Gamma rhythm refers to oscillatory neural activity between 30 and 80 Hz, which represents the interaction between different classes of neurons. Gamma in the primary visual cortex (V1) is generated intrinsically while presenting stimuli such as iso-luminant hues or gratings. Gamma is thought to be sensitive to interconnectivity patterns in the cortical area as its properties change with possible changes in cortical circuitry due to aging or mild cognitive impairment (MCI). The goal of my research is to model gamma generation in V1 to help understand the underlying circuitry. Gamma exhibits variations in power and frequency depending on the stimulus properties. Power and peak-frequency of gamma have been known to depend on the properties of the stimulus such as size and contrast. These stimulus-dependencies have been demonstrated in some models belonging to the class of ‘Wilson-Cowan’ (WC) models, which describe the interactions between excitatory and inhibitory populations. These models, while simplistic in structure and analytically tractable, are quite effective in describing neuronal population-level dynamics, and their sensitivity to perturbations in interconnectivity factors. In my work, we characterized the temporal structure of gamma rhythm in Local Field Potential (LFP) of macaque V1 and constrained the inputs to a WC model to emulate the temporal characteristics along with the stimulus-dependencies with size and contrast.